Engines operating with one or more cylinders as dedicated exhaust gas recirculation (EGR) cylinders can provide the entire EGR flow for the engine. The EGR flow can be provided to the intake manifold that feeds all the engine cylinders, including the dedicated EGR cylinder(s). The dedicated EGR cylinder(s) are typically run rich of a stoichiometric air-fuel ratio to provide reformed fuel products to the charge flow that feeds the engine cylinders. The reformed fuel products can enhance the flame speed and prevent the engine from knocking, allowing the engine to operate more efficiently.
However, during certain transient conditions and engine cranking, the EGR flow that is included in the charge flow to the engine cylinders can be significantly reduced or even result no EGR flow. For example, during engine cranking there is no EGR until combustion starts and the exhaust gas produced by the dedicated EGR cylinder(s) flows to the intake manifold. In another example, during accelerator tip-out and/or motoring conditions, the engine pumps fresh air through all the cylinders with no combustion, filling the intake manifold with fresh air. During a subsequent accelerator tip-in, the engine is momentarily more knock limited than during steady state operations since there is no EGR in the intake manifold. The spark timing in the engine cylinders is therefore retarded to prevent engine knock. However, this reduces engine efficiency. Therefore, further technological developments are desirable in this area.